AsyncUpload having 403 POST /Telerik.WebUI.WebResource.axd?type=rau

[Benjamin]

My asyncupload control is dynamically added during code runtime inside Page_Init. After my asyncupload validate success, the input is still showing red. opening the console i saw the error as shown in the attached file. Not sure if it is relevant, this code is created as a visual web part(farm solution) for Sharepoint 2016

 

i added the following to web.config

01.<httpHandlers>
02.     <add path="Telerik.Web.UI.DialogHandler.aspx" type="Telerik.Web.UI.DialogHandler" verb="*" validate="false" />
03.      <add path="Telerik.Web.UI.SpellCheckHandler.axd" type="Telerik.Web.UI.SpellCheckHandler" verb="*" validate="false" />
04.      <add path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" verb="*" validate="false" />
05.</httpHandlers>
06.
07.
08.<handlers>
09....
10. <add name="Telerik_Web_UI_DialogHandler_aspx" verb="*" preCondition="integratedMode" path="Telerik.Web.UI.DialogHandler.aspx" type="Telerik.Web.UI.DialogHandler" />
11.      <add name="Telerik_Web_UI_SpellCheckHandler_axd" verb="*" preCondition="integratedMode" path="Telerik.Web.UI.SpellCheckHandler.axd" type="Telerik.Web.UI.SpellCheckHandler" />
12.      <add name="Telerik_Web_UI_WebResource_axd" verb="*" preCondition="integratedMode" path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" />
13.</handlers>
14.
15.<location path="Telerik.Web.UI.WebResource.axd">
16.    <system.web>
17.      <authorization>
18.    <allow users="?"/>
19.      </authorization>
20.    </system.web>
21.  </location>
22.<location path="ScriptResource.axd">
23.    <system.web>
24.      <authorization>
25.    <allow users="?"/>
26.      </authorization>
27.    </system.web>
28.  </location>

[Benjamin]

to add-on the version of my telerik.web.ui.dll is 2020.3.1021.45